/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.tomcat.util.digester;

import org.xml.sax.Attributes;

/**
 * Rule implementation that creates a new object and pushes it
 * onto the object stack.  When the element is complete, the
 * object will be popped
 */

public class ObjectCreateRule extends Rule {


	// ----------------------------------------------------------- Constructors

	/**
	 * The attribute containing an override class name if it is present.
	 */
	protected String attributeName = null;
	/**
	 * The Java class name of the object to be created.
	 */
	protected String className = null;

	/**
	 * Construct an object create rule with the specified class name.
	 *
	 * @param className Java class name of the object to be created
	 */
	public ObjectCreateRule(String className) {

		this(className, (String) null);

	}

	/**
	 * Construct an object create rule with the specified class.
	 *
	 * @param clazz Java class name of the object to be created
	 */
	public ObjectCreateRule(Class<?> clazz) {

		this(clazz.getName(), (String) null);

	}

	// ----------------------------------------------------- Instance Variables

	/**
	 * Construct an object create rule with the specified class name and an
	 * optional attribute name containing an override.
	 *
	 * @param className     Java class name of the object to be created
	 * @param attributeName Attribute name which, if present, contains an
	 *                      override of the class name to create
	 */
	public ObjectCreateRule(String className,
	                        String attributeName) {

		this.className = className;
		this.attributeName = attributeName;

	}

	/**
	 * Construct an object create rule with the specified class and an
	 * optional attribute name containing an override.
	 *
	 * @param attributeName Attribute name which, if present, contains an
	 * @param clazz         Java class name of the object to be created
	 *                      override of the class name to create
	 */
	public ObjectCreateRule(String attributeName,
	                        Class<?> clazz) {

		this(clazz.getName(), attributeName);

	}


	// --------------------------------------------------------- Public Methods

	/**
	 * Process the beginning of this element.
	 *
	 * @param namespace  the namespace URI of the matching element, or an
	 *                   empty string if the parser is not namespace aware or the element has
	 *                   no namespace
	 * @param name       the local name if the parser is namespace aware, or just
	 *                   the element name otherwise
	 * @param attributes The attribute list for this element
	 */
	@Override
	public void begin(String namespace, String name, Attributes attributes)
			throws Exception {

		// Identify the name of the class to instantiate
		String realClassName = className;
		if (attributeName != null) {
			String value = attributes.getValue(attributeName);
			if (value != null) {
				realClassName = value;
			}
		}
		if (digester.log.isDebugEnabled()) {
			digester.log.debug("[ObjectCreateRule]{" + digester.match +
					"}New " + realClassName);
		}

		if (realClassName == null) {
			throw new NullPointerException("No class name specified for " +
					namespace + " " + name);
		}

		// Instantiate the new object and push it on the context stack
		Class<?> clazz = digester.getClassLoader().loadClass(realClassName);
		Object instance = clazz.newInstance();
		digester.push(instance);
	}

	/**
	 * Process the end of this element.
	 *
	 * @param namespace the namespace URI of the matching element, or an
	 *                  empty string if the parser is not namespace aware or the element has
	 *                  no namespace
	 * @param name      the local name if the parser is namespace aware, or just
	 *                  the element name otherwise
	 */
	@Override
	public void end(String namespace, String name) throws Exception {

		Object top = digester.pop();
		if (digester.log.isDebugEnabled()) {
			digester.log.debug("[ObjectCreateRule]{" + digester.match +
					"} Pop " + top.getClass().getName());
		}

	}

	/**
	 * Render a printable version of this Rule.
	 */
	@Override
	public String toString() {

		StringBuilder sb = new StringBuilder("ObjectCreateRule[");
		sb.append("className=");
		sb.append(className);
		sb.append(", attributeName=");
		sb.append(attributeName);
		sb.append("]");
		return (sb.toString());

	}


}
